Question: Factor completely. $5x^2-320=$
First, we take a common factor of $5$. $5x^2-320=5(x^2-64)$ Now, let's factor $x^2-64$. Both $x^2$ and $64$ are perfect squares, since $x^2=({x})^2$ and $64=({8})^2$. $x^2-64 = ({x})^2-({8})^2$ So we can use the difference of squares pattern to factor. ${a}^2 - {b}^2 =({a}+{b})({a}-{b})$ In this case, ${a}={x}$ and ${b}={8}$ : $({x})^2 - ({8})^2 =({x}+{8})({x}-{8})$ $\begin{aligned} 5x^2-320&=5(x^2-64) \\\\ &=5(x+8)(x-8) \end{aligned}$ In conclusion, the complete factorization is: $5(x+8)(x-8)$ Remember that you can always check your factorization by expanding it.